1. Field of the Invention
The present invention relates to a precision press device capable of transferring a micro structure with a high degree of flatness, and more particularly, to a precision press device applied to a micro structure transfer mold and a micro structure transfer device for pressing a matrix (micro structure transfer mold) which serves as a source with a micro uneven pattern formed on the surface against a target substrate (transfer target) for transferring/forming the micro uneven pattern onto the substrate surface and a press load control method thereof.
2. Description of the Related Art
As for the above described micro structure transfer devices, relatively low-cost nano-level imprinting devices are currently sold. The micro structure transfer devices are capable of nano-level transfer and those devices are generally called “nano imprinting devices.” Resin, glass or the like is mainly used as the material for the transfer targets, and devices based on the nano imprinting scheme are roughly classified into two categories depending on characteristics of those materials: optical nano imprinting devices using ultraviolet rays and thermal nano imprinting devices using heat. Furthermore, there are transfer schemes such as a parallel plate scheme using the principles of a general press device and a roller-type sheet nano device.
Here, during a transfer to a transfer target, the flatness and high accuracy of parallelism of a press stage section are particularly important for a parallel plate type nano imprinting device, and the uniformity of heat and pressure is also required. Furthermore, bubbles may be produced because press work is applied to the surface, and currently a transfer is generally performed in vacuum to avoid bubbles from mixing into the transfer target for both optical nano printing and thermal nano printing. Examples of current vacuum press devices include a scheme that performs press in a vacuum box as shown in FIG. 4, a scheme that mounts a sealing function using a spring or O-ring or the like near a press stage section and evacuates only the press stage and the pressurization section as described in Japanese Patent Laid-Open Publication No. 10-136943 or a scheme that performs press using an internal mechanism in vacuum with upper and lower housings contacting each other as described in Japanese Patent Laid-Open Publication No. 2003-181697.
In recent years, the parallel plate type devices are required to meet demands for not only downsizing, a cost reduction and task enhancement of the devices but also adaptability to transfer of materials a variety of sizes and types from small (20 mm per side) to large (φ300 mm).
As for the press scheme, there are devices using an air cylinder but servo press capable of easily realizing high-level control is becoming common. The nano imprinting devices themselves are mainly used in the semiconductor-related fields and are generally used in a clean room, and therefore not many devices adopt a hydraulic cylinder from the standpoint of dust generation and pollution.
In the case of a nano imprinting device capable of also large size (φ300) transfer, the use of a vacuum box results in a problem that the size of the device increases. Here, in view of downsizing of the device, devices with a sealing function provided in the vicinity of the press plate are considered effective. Here, a pressure fluctuation occurring in a chamber during evacuation will be considered. In a device capable of a large φ300 transfer, suppose the size of the room interior to be evacuated is φ300 and a pressure difference between the atmosphere and vacuum is approximately 0.1 MPa. A negative pressure equivalent to a load of approximately 720 kg is generated in the chamber until the press plate comes into contact.
Furthermore, in this device that allows large-size transfer, a negative pressure of only approximately 4 kg is produced when a small-size (20 mm per side) transfer is performed. No negative pressure is further produced in the area with which the transfer target is in contact, but the negative pressure is produced in the area with which the transfer target is not in contact in the vacuum chamber, and therefore there is a problem that a load of approximately 716 kg is placed on the small-size (20 mm per side). When a vacuum box is used, if the diameter of a sliding shaft is set to φ60 mm, a negative pressure of approximately 29 kg is produced. Here, even if an attempt is made to attain a balance with the negative pressure using a repulsive force of an O-ring or spring, the device becomes unusable if only the transfer target has a different size and thickness.
Here, to perform feedback control on the pressure, a pressure sensor is provided inside or outside the vacuum chamber of the nano imprinting device. However, since there is always a boundary between the chamber and movable shaft, there is a problem that an evacuation pressure in a vacuum condition to the diameter of the shaft or diameter of the chamber is produced on the pressurization axis as a negative pressure. Furthermore, the method whereby a pressure sensor is installed in the vacuum chamber also involves a problem that the chamber unit grows in size and complexity. Furthermore, there is also a problem that the negative pressure increases as the press stage and diameter of the shaft increase, and further the size of the transfer target also influences the pressure at the time of press work.
Furthermore, as for the above described micro structure transfer device, relatively low-cost nano-level imprinting devices are currently available on the market. The micro structure transfer devices can realize nano-level transfer and such devices are generally called “nano imprinting device.” Resin, glass or the like is mainly used as the material of the transfer target, and the nano imprint scheme is roughly classified under two categories depending on the characteristics of those materials; optical nano imprinting devices using ultraviolet rays and thermal nano imprinting devices using heat. Furthermore, examples of the transfer scheme include a parallel plate scheme using the principles of a general press device and a roller type sheet nano device.
Here, the flatness and parallelism of the press stage section are particularly important for the parallel plate type nano imprinting device. Examples of a parallelism adjusting mechanism for devices currently in use include a scheme whereby a spherical bearing mechanism is set up right below the press stage of any one of the pressurized side and the pressurizing side of the press mechanism so as to slide on the sphere and adjust the parallelism and a scheme whereby an elastic body such as a spring is attached right below the press stage.
In recent years, there are growing demands for upsizing and task enhancement of micro structure transfer devices. However, the increase in the size of parallel plate type nano imprinting devices is accompanied by problems like deterioration of the accuracy of flatness, parallelism or the like, and increased differences in the required pressure and temperature or the like depending on the size and material of the transfer target, thus widening the scope of application and making control more complicated.
As a press scheme, there are devices using an air cylinder, but devices using servo press that can easily realize high-level control are becoming popular. The nano imprinting devices are mainly used in the semiconductor-related fields and are generally used in a clean room, and therefore not many devices adopt a hydraulic cylinder from the standpoint of dust generation and pollution.
Among press machines that pressurize a part sandwiched between two opposing surfaces, there is a proposal of a press machine that rotatably supports a mold retention plate including one surface via a spherical bearing whose center is located on the normal to the surface, provides fixing means for stopping the rotation of the mold retention plate, attaches an elastic sheet to the one surface in an easily detachable manner, and thereby provides trackability (correction performance) to nonuniformity in the thickness of a pressurization target and allows the pressurized section to be separated and extracted (see Japanese Patent Laid-Open Publication No. 2005-52841).
Furthermore, there is a proposal of a press molding device that forms a surface of a lower molding die opposite to an optical surface from which a shape is transferred to a material into a convex spherical shape, forms a matrix that holds the lower molding die into a concave spherical shape corresponding to the spherical shape of the lower molding die, assumes the curvature center of the convex spherical surface and the concave spherical surface to be a position of the pressed molded product on the central axis of the molding die or a position within a range of the thickness of the molded product on the central axis from an end face of the molded product on the central axis, causes a body die to come into contact with an upper molding die at the time of press molding, and causes the lower molding die to swing, thereby causing the axial lines of both molding dies to match and automatically adjusting inclination (see Japanese Patent Laid-Open Publication No. 2003-54963).
Furthermore, in nano imprinting, there is a proposal of a transfer device and transfer method including matrix retaining means for retaining a matrix having a pattern corresponding to information, substrate retaining means for retaining a substrate to which the matrix pattern is transferred, fixing means for fixing a distance between the matrix and substrate, pressure applying means for applying a pressure between the matrix and substrate, and fixing canceling means interposed between the matrix retaining means and substrate retaining means and having an elastic body disposed around the matrix and substrate, for canceling the fixing the distance between the matrix and substrate by the fixing means and separating the matrix from the substrate, capable of uniformly applying a pressure to the matrix and substrate and easily separating the matrix from the substrate after a transfer (see Japanese Patent Laid-Open Publication No. 2002-100079).
However, when a heavy load is required or the size of the transfer target increases, as in the case of the nano printing technique according to Japanese Patent Laid-Open Publication No. 2005-52841 and Japanese Patent Laid-Open Publication No. 2003-54963, the structure whereby the load is received by a spherical surface causes the spherical mechanism itself to grow in size, increasing the possibility of producing friction, abrasion or a biting phenomenon. Furthermore, restoring the spherical bearing after having followed the inclination to its original horizontal condition requires an elastic body such as a spring to be used, which particularly complicates the mechanism in the vicinity of the press stage and further leads to upsizing and high cost. According to Japanese Patent Laid-Open Publication No. 2002-100079, when the load is received by a spring, the size of the spring increases to an extreme especially when the required load is large. There is also a problem that it is difficult to obtain uniform temperatures and temperature rise times are extended. Especially, it is essential that the surfaces of the pressurized section and the pressurizing section come into contact with the surface of the thermal nano printing press parallel to each other. However, it is extremely difficult to work the pressurizing section or the pressurized section with high accuracy and further work/adjust the guides of the pressurizing section and the pressurized section with high accuracy. To achieve highly accurate parallelism, various measures have been taken, for example, providing a spherical bearing right below the pressurizing section or pressurized section, using air or an equivalent fluid or elastic body as a cushion, adopting a link mechanism for the pressurized section and providing right below the press stage a mechanism for receiving a pressure in parallel. However, various elements such as a heater and cooling path need to be added to the press stage and there is a problem that most of such mechanisms are likely to grow in size and complexity.
In view of the above described technical problems, it is an object of the present invention to provide a micro structure transfer device (nano imprinting device) having a simple structure and capable of high accuracy pressure control in nano printing, which is a pattern transfer technique to form a micro structure.
Noticing the difficulty in work on parts and assembly on nano-level order and difficulty in a nano-level press because it is a press between rigid bodies, there are problems to be solved in absorbing the inclination and deflection on both sides of the matrix retaining side and the substrate retaining side with respect to a guide section that retains or slidably engages both sides to thereby enable a pressure to be applied to the matrix and the substrate uniformly.
It is therefore an object of the present invention to provide a micro structure transfer device having a simple structure around a press stage and providing an excellent way of adjusting parallelism in a nano printing method which is a pattern transfer technique including steps of manufacturing a product having a micro or ultra-micro processing pattern for forming a micro structure.